Ill put all the links at the bottom
Id say save up a bit more and go for the retina MacBook Pro because a fw months ago they dropped the prices and there amazing or just the standard macbook pro i have the standard and it is great for movie editing but the 11 inch air wouldn't be good for editing and doesn't have a big screen.
However you could also get a Mac Mini they are really good and there about £500 and you can just get a monitor for an extra one hundred and then get a mouse and keyboard i suggest getting the official apple keyboards as they work best because a windows one doesn't have all of the special buttons at th top of the keyboard and doesn't have the command button
Also the MacBooks are light and you can easily carry them around your right they are lightweight and i was amazed at how thing and light it was when i went to the apple store but the normal MacBooks aren't heave at all
Lastly You could get an iMac there very close in price to the retina Macbook Pro but they have amazing graphics a 21.5 inch screen and come with the keyboard and mouse and all the editing and look amazing
Links:
Retina MacBook Pro: http://www.apple.com/...cbook-pro/
Mac Mini: http://www.apple.com/.../mac-mini/
iMac: http://www.apple.com/...m/uk/imac/
MacBook Air: http://www.apple.com/...cbook-air/
There isn't an info page on the normal Macbook but here is the spec page:
http://store.apple.com/...tep=config
iMovie: http://www.apple.com/...ac/imovie/
Also with iMovie if you decide you want to go more into the video editing you can upgrade to final cut pro an all your iMovie stuff will sync with your final cut pro and also you could go down the Adobe route
Mac Apple Store: http://store.apple.com/...com/uk/mac
Hope this helps